1. Depends on the car, the type of system used and the drive cycle of the car. Cars run for short distances will need more fuel to regenerate their DPFs than cars driven long distances where the DPF naturally burns off the soot. 2. No 'typical' lifespan. They are common failures on Volkswagens, Citroens and Rover 75s. 3. Independent specialists used to reckon about 80,000 miles before they started to dribble. 4. It's because Piezo injectors are very precise and this makes them vulnerable to bad fuel.